clean up design

app.py

@@ -196,7 +196,7 @@ def render_idx(docs, idx: int):
     idx = max(0, min(idx, len(docs) - 1))
     doc = docs[idx]
     left, left_meta, md, info, right, header = show_doc(doc)
-    return left, left, left_meta, md, info, right, header
+    return left, left_meta, md, info, right, header
 
 
 def on_prev(docs_cache, idx: int, reader_iter, require_has_math: bool, require_has_infobox: bool):